The Turks and the Arabs.—Meanwhile, about A.D. 56o, a new nation had sprung up in the East, the Turks. Chosroes con cluded an alliance with them against the Ephthalites and so conquered Bactria south of the Oxus, with its capital Balkh. Thus this province, which, since the insurrection of Diodotus in 25o B.C., had undergone entirely different vicissitudes from the rest of Iran, was once more united to an Iranian empire, and the Sassanid dominions, for the first time, passed the frontiers of the Arsacids. This, however, was the limit of their expansion. Neither the territories north of the Oxus, nor eastern Afghanistan and the Indus provinces, were ever subject to them. That the alliance with the Turks should soon change to hostility and mutual at tack was inevitable from the nature of the case ; in the second Roman war the Turkish Khan was leagued with Rome.
Chosroes bequeathed this war to his son Hormuzd IV. (579— 590) who, in spite of repeated negotiations, failed to re-establish peace. Hormuzd had not the ability to retain the authority of his father, and he further affronted the Magian priesthood by declining to proceed against the Christians and by requiring that, in his empire, both religions should dwell together in peace. Eventually, he succumbed to a conspiracy of his magnates, at whose head stood the general Bahram Cobin, who had defeated the Turks, but afterwards was beaten by the Romans. Hormuzd's son, Chosroes II., was set up against his father and forced to acquiesce in his execution. But immediately new risings broke out, in which Bahram Cobin—though not of the royal line—at tempted to secure the crown, while simultaneously a Prince Bis tam entered the lists. Chosroes fled to the Romans and the em peror Maurice undertook his restoration at the head of a great army. The people flocked to his standard ; Bahram Cobin was routed (591) and fled to the Turks, who slew him, and Chos roes once more ascended the throne of Ctesiphon ; Bistam held out in Media till 596. Maurice made no attempt to turn the opportunity to Roman advantage, and in the peace then con cluded he even abandoned Nisibis to the Persians.
Chosroes II. (59o-628) is distinguished by the surname of Parvez ("the conqueror"), though, in point of fact, he was im measurably inferior to a powerful sovereign like his grandfather, or even to a competent general. He lived, however, to witness unparalleled vicissitudes of fortune. The assassination of Maurice in 602 impelled him to a war of revenge against Rome, in the course of which his armies—in 6o8 and, again, in 615 and 626— penetrated as far as Chalcedon opposite Constantinople, ravaged Syria, reduced Antioch (611), Damascus (613), and Jerusalem (614), and carried off the holy cross to Ctesiphon; in 619 Egypt was occupied. Meanwhile, the.Roman empire was at the lowest ebb. The great emperor Heraclius, who assumed the crown in 610, took years to create the nucleus of a new military power. This done, however, he took the field in 623, and repaid the Persians with interest. Their armies were everywhere defeated. In 624 he penetrated into Atropatene (Azerbaijan), and there de stroyed the great fire-temple; in 627 he advanced into the Tigris provinces. Chosroes attempted no resistance, but fled from his residence at Dastagerd to Ctesiphon. These proceedings, in con junction with the avarice and licence of the king, led to revolu tion. Chosroes was deposed and slain by his son Kavadh II.
(628) ; but the parricide died in a few months and absolute chaos resulted. A whole list of kings and pretenders—among them the General Sharbaraz and Boran, a daughter of Chosroes—f ollowed rapidly on one another, till finally the magnates united and, in 632, elevated a child to the throne, Yazdegerd III., grandson of Chosroes. In the interval—presumably during the reign of Queen Boran—peace was concluded with Heraclius, the old frontier being apparently restored. The cross had already been given back to the emperor.
Thus the i oo years' struggle between Rome and Persia, which had begun in 527 with the attack of the first Kavadh on Justinian, had run its fruitless course, utterly enfeebling both empires and consuming their powers. Room was given to a new enemy who now arose between either state and either religion—the Arabs and Islam. In the same year that saw the coronation of Yazdegerd iii.—the beginning of 633—the first Arab squadrons made their entry into Persian territory. After several encounters there en sued (637) the battle of Kadisiya (Qadisiya, Cadesia), fought on one of the Euphrates canals, where the fate of the Sassanian empire was decided. A little previously, in the August of 636, Syria had fallen in a battle on the Yarmuk (Hieromax), and in 639 the Arabs penetrated into Egypt. The field of Kadisiya laid Ctesiphon, with all its treasures, at the mercy of the victor. The king fled to Media, where his generals attempted to organize the resistance; but the battle of Nehavend (641) decided mat ters there. Yazdegerd sought refuge in one province after the other, till, at last, in 651, he was assassinated in Mery (see CALIPHATE : §A, Thus ended the empire of the Sassanids, no less precipitately and ingloriously than that of the Achaemenids. By 65o the Arabs had occupied every province to Balkh and the Oxus. Only in the secluded districts of northern Media (Tabaristan), the "gen erals" of the house of Karen (Spahpat, Ispehbed) maintained themselves for a century as vassals of the caliphs—exactly as Atropates and his dynasty had done before them.
The fall of the empire sealed the fate of its religion. The Muslims officially tolerated the Zoroastrian creed, though oc casional persecutions were not lacking. But little by little it vanished from Iran, with the exception of a few remnants (chiefly in the oasis of Yezd), the faithful finding a refuge in India at Bombay. These Parsees have preserved but a small part of the sacred writings; but to-day they still number their years by the era which begins on June 16, A.D. 632, with the death of Yazde gerd III., the last king of their faith and the last lawful sovereign of Iran, on whom rested the god-given Royal Glory of Ormuzd.
BIBLIOGRAPHY.—Besides the works on special periods quoted above, the following general works should be consulted: Spiegel, Eranische Altertumskunde (3 vols., 1876 sqq.) ; W. Geiger and Ernst Kuhn, Grundriss der iranischen Philologie herausg., vol. ii. (Literature, History and Civilization, 1896 sqq.) ; G. Rawlinson, The Five Great Monarchies, The Sixth Monarchy, The Seventh Monarchy. Further the mutually supplementary work of Th. Noldeke, Aufsiitze zur persischen Geschichte (1887, Medes, Persians and Sassanids), and A. v. Gutschmid, Geschichte Iran von Alexander d. Gr. bis zum Untergang der Arsaciden (1888). A valuable work of reference is F. Justi, Iranisches Namenbuch (1895). See also ROME; GREECE;